An effective method for the preparation of a block copolymer offers one the opportunity to modity the copolymer with monomers which are normally incompatible. Thus the process permits the chemical union of two incompatible macromolecules which would otherwise be difficult to link. A successful process for synthesis of a block copolymer requires a reliable polymerization process which is not hindered by the usual problems of linking already formed polymer chains.
It was the hope that a phase transfer catalyzed (PTC) reaction would lend itself to the synthesis of desirable polymers and free the process from the use of anhydrous aprotic solvents, which led me to exploit the particular characteristics of a PTC reaction for the purpose at hand. In nucleophilic displacement step-growth polymerizations, for example in the synthesis of polyethers and polycarbonates, these characteristics are as follows: (a) the reaction is very fast, reaching 100% yield and high molecular weight (mol wt) in a few minutes; (b) the polymer's mol wt does not depend strongly on the ratio between the nucleophilic and electrophilic reactants as in conventional step polymerizations; and, (c) the obtained polymer almost always contains electrophilic species as chain ends, independent of the reaction yield and reactant ratio.
It is hypothesized that the etherification reaction occurs in the organic phase according to a mechanism similar to that of interfacial polycondensation. The concentration of reactive bisphenolate in the organic phase is controlled by the concentration of the PTC and is very low in comparison with that of the electrophilic monomer. I eventually came to realize that PTC reactions can be exploited as a simple method for the synthesis of telechelic polymers containing electrophilic chain ends. These polymers with functional electrophilic end groups are useful polymeric materials because they can be further used as macroinitiators for cationic polymerization and for synthesis of ordered and block copolymers by condensation polymerization in the presence of a PTC.
The particular interest of this invention is to tailor an (A)(B) type block copolymer of polyarylene polyether ("PAPE") segments so that the block copolymer exhibits desired properties, for example, the ability to withstand thermal degradation at a temperature in the range from above 100.degree. C. to about 200.degree. C.
This invention is more particularly related to block copolymers formed by combining a PAPE segment A having phenolic (Ph) or thiophenolic (TPh) chain ends with a PAPE segment B having haloallylic chain ends. Segment A consists essentially of polymers of dihydroxybenzene, dihydroxynaphthalene, and diphenols, all referred to herein as dihydric phenols ("DHP"), and the corresponding sulfur (thio) compounds referred to as dihydric thiophenols ("DHTP"), which polymers have a Mn (number average mol wt) less than about 10,000, hence termed oligomers. One or the other DHP and DHTP, or both, are referred to herein as "DH(T)P" for brevity. Such oligomers are defined herein as polymers containing from 2 to about 100 repeating units each having the formula --DH(T)P.sub.1 --DH(T)P.sub.2 --, where DH(T)P.sub.1 and DH(T)P.sub.2 each represents the residue of a DH(T)P. These oligomers contain at least three phenyl or thiophenyl rings which may have inert substituents, each ring linked to another through an O, Si, C or S atom. Such DHP and DHTP oligomers, also, poly[DH(T)P], or [DH(T)P].sub.n, are terminated at each end (hence "di-terminated") with a phenol ("Ph") or thiophenol ("TPh") group respectively, which group may also have inert substituents. For brevity, "di-(T)Ph-terminated" refers herein to either or both oligomers which are Ph- and TPh-terminated respectively, the preparation of which oligomers is described in detail in my copending U.S. patent application Ser. No. 586,678, now U.S. Pat. No. 4,562,243, the disclosure of which is incorporated by reference thereto as if fully set forth herein.
Specific alternating block copolymers and regular (chain extended) polymers and details of their preparation, analyses of the copolymers obtained, and a discussion of various aspects of their preparation and results of the analyses, are provided in an article titled "Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis. 6. On the Transfer Catalyzed Williamson Polyetherification as a New Method for the Preparation of Alternating Block Copolymers" by Virgil Percec, Brian C. Auman and Peter L. Rinaldi, Polymer Bulletin 10, 391-396 (1983), and in another article titled "Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis, 1.--Alternating Block Copolymers of Unsaturated Polyethers and Aromatic Poly(ether sulfone)s" by Virgil Percec and Brian C. Auman, Makromol. Chem. 185 617-627 (1984), the disclosures of which articles and relevant portions of the references cited therein are incorporated by reference thereto as if fully set forth herein.